Down-regulation of miR-200b-targeting Slug axis by cyclosporine A in human gingival fibroblasts

Background/Purpose: Cyclosporine A (CsA) has been used as an immunosuppressive agent with a side effect of gingival overgrowth. It has been known that CsA-induced epithelial-mesenchymal transition (EMT) in gingiva, but the molecular mechanism has not been fully unveiled. The purpose of the study is to investigate functional roles of microRNAs in gingival overgrowth. Methods: The effect of CsA on the expression of microRNA-200b (miR-200b) in normal human gingival fibroblasts (HGFs) was determined using qRT-PCR. Luciferase reporter assay and Western blot were utilized to examine the relationship between miR-200b and EMT inducer Slug. Cell proliferation was assessed by MTT assay. Results: CsA was found to downregulate the miR-200b transcript in HGFs in a dose-dependent manner. Luciferase reporter assay confirmed that Slug was a direct target of miR-200b, and the CsA-induced cell proliferation and Slug upregulation were inhibited by overexpression of miR-200b. Additionally, the silence of Slug reversed the increased proliferation of HGFs by miR-200b inhibitor. Conclusion: Repression of miR-200b after CsA administration led to an increase in Slug expression. Our results suggested that miR-200b was an upstream effector of the CsA-induced EMT and may act as a therapeutic target for CsA-induced gingival overgrowth.